UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS, 

COLLEGE  OF  AGRICULTURE. 

AGRICULTURAL  EXPERIMENT  STATION. 

BERKELEY,  CALIFORNIA. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE 


By  FREDERIC  T.  BIOLETTI 


EFFECT  OF  OIDIUM  ON  YOUNG   GROWTH. 


BULLETIN     NO.    186 

(February,  1907) 


BERKELEY 
THE  UNIVERSITY  PRESS 


Benjamin  Ide  Wheeler,  Ph.D.,  LL.D.,  President  of  the  University. 

EXPEEIMENT  STATION  STAFF. 

E.  J.  Wickson,  M.A.,  Acting  Director  and  Horticulturist. 

E.  W.  Hilgard,  Ph.D.,  LL.D.,  Chemist. 

W.  A.  Setchell,  Ph.D.,  Botanist. 

Elwood  Mead,  M.S.,  C.E.,  Irrigation  Engineer. 

C.  W.  Woodworth,  M.S.,  Entomologist. 

E.  H.  Loughridge,  Ph.D.,  Agricultural  Geologist  and  Soil  Physicist.  (Soils  and 
Alkali.) 

M.  E.  Jaffa,  M.S.,  Nutrition  Expert,  in  charge  of  the  Poultry  Station. 

G.  W.  Shaw,  M.A.,  Ph.D.,  Agricultural  Technologist,  in  charge  of  Cereal  Stations. 

George  E.  Colby,  M.S.,  Chemist.  (Fruits,  Waters,  Insecticides.)  (Absent  on 
leave.) 

Ralph  E.  Smith,  B.S.,  Plant  Pathologist  and  Superintendent  of  Southern  Cali- 
fornia Pathological  Laboratory  and  Experiment  Stations. 

A.  E.  Ward,  B.S.A.,  D.V.M.,  Veterinarian  and  Bacteriologist. 

E.  W.  Major,  B.Agr.,  Animal  Industry. 

F.  T.  Bioletti,  M.S.,  Viticulturist.     (Grapes,  Wine,  and  Zymology.) 
n.  M.  Hall,  M.S.,  Assistant  Botanist. 

H.  J.  Quayle,  A.B.,  Assistant  Entomologist. 

John  S.  Burd,  B.S.,  Chemist  in  charge  of  Fertilizer  Control. 

C.  M.  Haring,  D.V.M.,  Assistant  Veterinarian  and  Bacteriologist. 
E.  H.  Smith,  M.S.,  Assistant  Plant  Pathologist. 

H.  J.  Eamsey,  M.S.,  Assistant  Plant  Pathologist. 

T.  F.  Hunt,  B.S.,  Assistant  Plant  Pathologist. 

E.  E.  Mansell,  Assistant  in  Horticulture,  in  charge  of  Central  Station  Grounds. 

G.  E.  Stewart,  B.S.,  Assistant  in  Station  Chemical  Laboratory. 
,  Assistant  in  Soil  Laboratory. 

Ealph  Benton,  B.S.,  Assistant  in  Entomology. 

Ludwig  Eosenstein,  Laboratory  Assistant  in  Fertilizer  Control. 

Alfred  Tournier,  Assistant  in  Viticulture. 

Hans  Holm,  Student  Assistant  in  Zymology. 

A.  J.  Gaumnitz,  Assistant  in  Cereal  Laboratory. 

J.  C.  Bradley,  A.B.,  Assistant  in  Entomology. 

D.  L.  Bunnell,  Clerk  to  the  Director. 


John  Tuohy,  Patron      ) 

J.  T.  Bearss,  Foreman  }  Tulare  Sub-Station,  Tulare. 

J.  W.  Mills,  Horticultural  Assistant  in  Southern  California,  Eiverside. 

J.  W.  Eoper,  Patron         ) 

E.  C.  Miller,  In  charge  }  UniversitJ  Forestry  Station,  Chico. 

Eoy  Jones,  Patron  ) 

N.  D.  Ingham,  Foreman  j  University  Forestry  Station,  Santa  Monica. 

Vincent  J.  Huntley,  Foreman  of    California  Poultry  Experiment  Station,  Peta- 
luma. 

The  Station  publications   (Reports  and  Bulletins),  so  long  as 
available,  will  be  sent  to  any  citizen  of  the  State  on  application. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE. 


.  Fungous  Diseases  of  the  Vine.  California  is  peculiarly  fortunate 
in  its  freedom  from  most  of  the  serious  fungous  vine  diseases  which 
add  so  much  to  the  expense  and  uncertainty  of  grape  growing  in  most 
countries.  Peronospora,  Black  Rot,  and  Anthracnose  are  here  quite 
unknown.  Of  the  four  most  serious  fungous  diseases  which  attack  the 
above-ground  portions  of  the  vine,  these  three  are  the  most  to  be  feared, 
as  they  are  not  only  capable,  if  neglected,  of  destroying  the  whole  crop 
of  a  vineyard,  but  require  the  utmost  vigilance  and  much  troublesome 
treatment  with  winter  washes  and  summer  sprays  to  hold  them  in 
check.  Their  absence  makes  quite  unnecessary  the  swabbing  of  the 
dormant  vines  with  sulfate  of  iron  and  the  spraying  of  the  growing- 
vines  with  Bordeaux  mixture  which  are  adopted  here  by  some  vine- 
yardists  who  have  learned  the  practice  in  Europe  or  the  Eastern  States 
where  it  is  necessary. 

On  the  other  hand,  the  remaining  serious  fungous  disease — Oidium 
— exists  in  all  parts  of  California.  From  one  point  of  view,  this  is  the 
most  serious  disease  of  the  four,  as,  if  uncontrolled,  it  is  capable  of 
spreading  more  universally  through  the  vineyards  and  of  absolutely 
destroying  the  crops  in  nearly  all.  From  another  point  of  view,  it  is 
the  least  to  be  feared,  as  it  is  possible  to  control  it  completely,  at  least 
in  most  parts  of  California,  by  much  simpler  and  less  expensive  meth- 
ods than  are  needed  for  the  others  mentioned. 

Introduction  of  Oidium  into  Europe.  With  the  exception  of  An- 
thracnose, which  is  a  native  of  Europe,  all  these  diseases  originated  on 
the  wild  vines  of  the  Eastern  and  Central  parts  of  the  United  States. 
Peronospora  and  Black  Rot  are  comparatively  recent  introductions 
into  Europe.  The  former  was  observed  for  the  first  time  in  1878,  the 
latter  not  until  1885.  The  Oidium  was  first  noted  in  Europe  about 
1845,  when  an  English  gardener  named  Tucker  found  it  in  graperies 
at  Margate,  near  the  mouth  of  the  Thames.  It  was  discovered  two 
years  later  in  the  hot-houses  of  Paris  and  Belgium. 

Severity  of  the  Disease  in  Europe.  From  this  time  it  spread  rap- 
idly, until  by  1851  it  had  reached  every  grape-growing  country  of 
Europe.  The  amount  of  injury  done  by  the  disease  was  enormous  and 
increased  every  year,  reaching  its  maximum  in  France  about  1854.    In 


v 


316  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 

this  year  it  reduced  the  crop  of  grapes  in  France  over  75  per  cent.,  in 
many  districts  totally  destroying  the  crop. 

Discovery  of  the  Utility  of  Sulfur.  After  1854,  the  grape  growers 
of  France  commenced  to  learn  how  to  control  the  disease.  The  use  of 
sulfur  for  this  purpose,  discovered  and  perfected  between  1850  and 
1853,  soon  became  general,  and  by  1859  the  crop  of  grapes  had  reached 
its  normal  volume  in  France.  The  effect  of  Oidium  in  diminishing  the 
crop  and  the  effect  of  sulfur  in  controlling  the  disease  in  one  depart- 
ment of  France  is  well  shown  by  fig.  1.  This  figure,  which  is  adapted 
from  one  published  in  the  nursery  catalogue  of  F.  Richter,  Montpellier, 
indicates  also  the  destruction  of  French  vineyards  by  Phylloxera  and 
their  rehabilitation  by  means  of  resistant  vines.  The  rapidity  with 
which  sulfur  enabled  the  French  grape  growers  to  reestablish  their 
vineyards  is  in  contrast  with  the  slower  process  of  controlling  the  phyl- 
loxera. In  three  or  four  years  after  the  use  of  sulfur  became  general 
in  the  Kerault  the  crops  had  reached  their  normal  volume.  It  has 
taken  twenty  years  to  reestablish  the  same  vineyards  on  phylloxera 
resistant  stocks. 


'  9jt9 

/yo* 

OiDlUM 

SULFUR 

PHYLLOXERA            ^T 

I8S0               f 

^<      ^T          VINES 

t*56 

\/r£SISTA(\IT 

1  8$5 

Fig.  I.  Showing  (1)  the  reduction  of  crop  of  wine  in  the  Herault  from  3,900,000 
hectoliters  in  1850  to  1,000,000  hectoliters  in  1856  by  the  attack  of  Oidium; 
(2)  the  rapid  increase  of  crop  after  the  general  use  of  sulfur;  (3)  the  re- 
duction by  phylloxera  of  the  crop  from  15,200,000  hectos  in  1869  to  2,100,- 
000  hectos  in  1885;  and  (4)  the  gradual  increase  due  to  the  use  of  resistant 
vines.     - 

Damage  clone  by  the  Disease  in  California.  In  California  the 
Oidium  has  never  produced  such  wide-spread  and  serious  injury  as 
that  indicated  above.  This  arises  principally  from  the  dryness  and 
heat  of  the  atmosphere  during  summer  in  most  of  our  grape-growing 
regions.     The  dryness  of  our  climate  is  undoubtedly  the  cause  of  our 


OIDIUM  OK  POWDERY  MILDEW  OF  THE  VINE.  317 

immunity  to  Peronospora,  Anthracnose,  and  Black  Rot,  and  while 
Oidium  requires  less  moisture  than  these  diseases  for  its  development, 
it  spreads  more  rapidly  and  is  more  difficult  to  control  in  a  moist  at- 
mosphere than  in  a  dry  one. 

At  the  same  time,  the  Oidium  does  far  more  harm,  even  in  Cali- 
fornia, than  is  usually  suspected,  and  in  certain  regions  and  certain 
seasons  may  totally  destroy  the  crop  and  diminish  the  crops  of  follow- 
ing years  by  injuring'  the  vine. 

There  has  been  a  recrudescence  of  the  intensity  of  this  disease  both 
in  Europe  and  California  during  the  last  few  years.  This  is  due  in  all 
probability  not  to  any  change  in  the  fungus  or  of  the  seasons,  as  has 
been  suggested,  but  to  the  neglect  of  regular  sulfuring  by  the  grape 
growers,  who  have  become  careless  after  years  of  comparative  immu- 
nity due  to  more  or  less  general  treatment  for  the  disease. 

While  most  grape  growers  in  California  sulfur  their  vines  in  some 
way,  many  of  them  do  not  succeed  in  completely  controlling  the  disease 
and  are  often  doubtful  of  the  utility  of  the  treatment.  Where  good 
.sulfur  does  not  give  immunity  it  is  because  it  has  not  been  applied  in 
the  right  way  or  at  the  right  time.  Many  growers  who  do  succeed  in 
keeping  their  vines  free  from  Oidium  do  so  at  the  expense  of  far  more 
sulfur  and  labor  than  are  necessary. 

The  main  object  of  this  bulletin,  therefore,  is  to  point  out  the  meth- 
ods of  control  which  have  been  generally  found  the  best  and  least 
costly. 

DESCRIPTION  OF  THE  DISEASE. 

RelationsJiips  of  the  Disease.  This  disease,  usually  called  Mildew 
in  California,  is  caused  by  a  fungus  belonging  to  the  same  group  as  the 
fungi  which  cause  the  mildews  of  roses,  hops,  beans,  and  apples  and  is 
generally  referred  to  as  Oidium  in  Europe.  The  disease  known  as 
Mildew  or  Peronospora  in  Europe  and  the  East  is  totally  different  and 
caused  by  a  fungus  of  very  different  character.  In  order  to  distinguish 
the  two,  the  Oidium  is  sometimes  called  Powdery  Mildew  and  the 
Peronospora,  Downy  Mildew.  As  only  one  exists  in  California,  the 
use  of  the  word  Mildew  should  lead  to  no  confusion,  though  perhaps  it 
is  best  to  adopt  Oidium  as  the  name  of  this  disease. 

Symptoms  and  Effect  on  the  Tine.  The  Oidium  attacks  all  her- 
baceous parts  of  the  vine, — leaves,  canes,  flowers,  and  fruit.  In  the 
spring,  the  young  leaves  which  are  attacked  show  at  first  whitish 
patches  about  one-quarter  of  an  inch  in  diameter  on  the  upper  or  lower 
surfaces.     (See  fig.  2.) 


'318 


UNIVERSITY   OF  CALIFORNIA EXPERIMENT   STATION. 


As  the  disease  progresses  these  patches  run  together  until  a  large 
part  of  the  surface  of  the  leaf  may  be  covered  with  a  grayish  white 
mildew.  The  leaf  ceases  to  grow  and  curls  up  towards  its  upper  sur- 
face.    (See  figure  on  cover.) 


Pig.  2.     White  patches  of  Oidium  on  upper  surface  of  young  leaf. 

As  the  shoots  lengthen,  the  canes  may  be  attacked  in  the  same  way. 
The  patches  of  mildew  appear  usually  near  the  bases  of  the  canes  and 
are  difficult  to  see  until  they  acquire  the  gray  tint.  In  severe  cases,  the 
fungus  may  completely  cover  the  whole  surface  of  the  cane,  but  it  is 
usually  confined  to  patches.  If  these  patches  are  rubbed  the  fungus 
comes  off  completely.  The  places  where  it  has  been,  however,  will  turn 
dark  later  owing  to  injuries  to  the  superficial  cells  of  the  bark.  (See 
fig.  3.) 


Fig.  3.     Blackening  of  canes  due  to  Oidium. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE. 


319 


These  marks,  at  first  brown,  later  black,  are  usually  branching  or 
fern-like  in  form,  showing  the  points  of  attack  of  the  fungus.  If  the 
canes  are  attacked  when  young,  they  fail  to  mature  properly  and  often 
turn  black  over  their  whole  surface.  It  is  this  form  of  Oidium  which 
has  sometimes  been  mistaken  for  Anthracnose  in  California. 

Later,  the  blossoms  and  fruit  may  be  attacked.  When  the  blossoms 
are  attacked  they  fail  to  set,  and  if  the  berries  are  attacked  when  very 
small,  they  will  fail  to  develop  and  will  drop  off.  If  the  fruit  reaches 
nearly  full  size  before  being  affected,  it  continues  to  develop,  but  irreg- 
ularly. The  parts  of  the  epidermis  injured  by  the  fungus  become  hard- 
ened and  cease  to  grow.  This  results  in  irregularity  in  the  form  of  the 
berry  and  in  severe  cases  in  cracking.     (See  fig.  4.) 


Fig.  4.     Berries  badly  affected  and  cracked.     (After  Foex.) 


If  this  cracking  occurs  early,  the  grapes  dry  up  completely  before 
ripening.  If  later,  they  may  develop  sugar  and  can  be  used  for  wine 
making,  but  the  crop  is  diminished  in  volume.  In  moist  seasons  the 
berries  which  are  cracked  usually  become  the  prey  of  blue  mould  and 
are  completely  destroyed. 

After  the  grapes  have  lost  the  green  color  due  to  the  presence  of 
chlorophyll  in  the  skin  and  have  commenced  to  ripen  they  are  not  at- 
tacked by  Oidium.  The  markings  and  blotches  which  are  often  seen 
on  ripe  grapes  are  due  to  injuries  to  the  skin  caused  by  the  presence 
of  the  fungus  on  the  grapes  before  they  ripened.  If  the  attack  has  not 
been  early  or  serious  enough  to  prevent  the  grapes  reaching  normal 


320  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT   STATION. 

size  they  may  still  make  good  wine.  The  markings,  however,  are  very 
objectionable  on  table  and  raisin  grapes  and  decrease  their  value. 

Tokay  and  Muscat  grapes  often  show  the  dark,  fern-like  markings 
characteristic  of  the  disease  similar  to  those  shown  on  the  canes.  (See 
fig.  3.)  When  abundant,  these  markings,  which  are  accompanied  by  a 
thickening  of  the  skin,  injure  the  appearance  of  the  raisins.  Where 
the  skin  of  the  Muscat  grape  has  been  attacked  by  Oidium  it  will  re- 
main smooth  after  drying  and  not  show  the  fine  wrinkling  character- 
istic of  the  finest  raisins. 

A  vine  of  which  the  leaves  are  badly  attacked  has  a  peculiar  color 
and  wilted  appearance.  (See  figure  on  cover.)  This  appearance  is 
only  shown  when  the  conditions  of  temperature  and  moisture  are  favor- 
able to  the  growth  of  the  fungus  on  the  exterior  leaves.  This  can  occur 
only  at  the  beginning  of  the  season  in  the  warmer  and  drier  parts  of 
the  State.  When  the  air  is  hot  and  dry  the  fungus  cannot  grow  on  the 
outer  leaves.  The  proper  favorable  conditions,  however,  may  still  exist 
in  the  interior  of  the  vine.  For  this  reason  vines  may  look  perfectly 
healthy  from  a  little  distance,  while  the  fruit  and  the  bases  of  the  canes 
may  be  covered  with  Oidium.  A  vine  which  is  badly  attacked  has  a 
moldy  smell  readily  perceptible  to  many  people. 

DESCRIPTION  OF  THE  FUNGUS. 

Mode  of  Attack.  The  botanical  name  of  the  fungus  is  Uncinula 
spiralis  (Berkeley  and  Cooke),  and  it  belongs  to  the  family  or  group 
of  Erysipheae.  All  the  members  of  this  family  are  parasites  which 
live  upon  the  outer  surfaces  of  leaves  and  other  green  organs  of  plants. 
The  white  "mildeiv"  which  they  form  on  these  surfaces  consists  of  the 
branching  threads  or  mycelium,  which  constitute  the  vegetative  body 
of  the  fungus.  This  mycelium  grows  only  on  the  surface,  unlike  the 
mycelia  of  Peronospora  and  other  parasitic  fungi  which  enter  the  tis- 
sues of  the  host  plant.  It  obtains  its  nourishment  from  the  epidermal 
cells  of  the  plant  attacked,  by  means  of  suckers — haustoria — which 
penetrate  these  outer  cells.  The  outer  cells  thus  attacked  become  dark 
colored.  The  fact  that  the  Oidium  does  not  penetrate  the  tissues  of  the 
vine  much  facilitates  its  control  and  renders  its  destruction  possible  at 
any  stage  without  injury  to  the  host  plant  from  the  remedies  applied. 

Summer  Form  of  the  Fungus.  The  mycelial  threads  of  the  Unci- 
nula spiralis  are  extremely  fine — not  over  two  ten-thousandths  of  an 
inch  in  diameter.  They  elongate  and  grow  over  the  surface  to  which 
they  are  attached  by  their  haustoria  and  at  intervals  send  out  upright 
branches — hyphae — thirty   to   forty   ten-thousands   of   an   inch   long. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE. 


321 


Fig.  5.     Various  forms  of  Uncinula  spiralis. 
I,  II.     Perithecia  showing  /,  appendages,  and  a,  asci. 
III.     Summer  form  showing  m,  mycelium ;  t,  hyphae ;  c,  conidia;  and  h,  haustoria. 
IV.     Group  of  asci  removed  from  perithecium  emitting  s,  ascospores.     (Ill  and 
IV,  after  Viala.) 
V.     Summer  form  of  Oidium  as  it  appears  on  surface  of  leaf. 
VI.     Ditto  showing  effect  of  sulfur  (d).     (V  and  VI,  after  Mares.) 


322 


UNIVERSITY   OF  CALIFORNIA — EXPERIMENT  STATION. 


These  hyphae  are  somewhat  thicker  than  the  mycelial  threads,  grad- 
ually increasing  in  diameter  from  the  bottom  to  the  top  until  they 
become  two  or  three  times  as  thick  as  the  threads  from  which  they 
arise.  Cross  partitions  divide  the  hyphae  into  several  cells,  the  upper- 
most of  which  finally  becomes  detached  and  forms  a  conidium  or 
summer  spore.  The  hypha  continues  to  grow  and  the  second  cell  de- 
velops into  another  conidium.  This  process  continues  as  long  as  the 
conditions  are  favorable  throughout  the  summer,  each  hypha  produc- 
ing a  large  number  of  conidia.  These  conidia  are  egg-shaped  and 
measure  about  5  X  12  ten-thousandths  of  an  inch. 

When  a  conidium  falls  on  a  suitable  part  of  the  vine  it  sends  out  a 
germinating  tube  which  fixes  itself  by  haustoria  and  grows  into  a  new 
mycelium  which  in  turn  produces  more  summer  spores.  (See  fig.  5, 
IIIc.) 

In  this  way,  all  the  green  parts  of  a  whole  vine  may  finally  be 
covered  with  a  coating  of  mycellium,  hyphae,  and  conidia,  which  to- 
gether form  the  whitish  or  grayish  matter  we  know  as  "31ildew"  or 
Oidium. 

Winter  or  Resting  Forms.  In  .the  autumn  another  form  of  the 
fungus  is  often  produced.  Among  the  felted  threads  of  the  mycelium 
may  be  seen  with  the  unaided  eye  numerous  round  black  bodies,  which 
are  perithecia,  or  receptacles  containing  the  spores.  These  bodies  have 
an  average  diameter  of  about  ^50  of  an  inch,  wThich  is  about  one-third 
the  diameter  of  the  dot  of  an  i  in  the  print  of  this  bulletin.  (See  fig. 
6,A,B.) 

Under  the  microscope  they  are  seen  to  vary  in  color  from  yellow 
when  unripe  to  nearly  black  when  mature.     (See  fig.  7.) 


A  B 

Fig.  6.     Photomicrographs  of  Perithecia  on  Surface  of  Leaf. 
A.  Magnified  8  times.     B.  Magnified  35  times. 


OIDIUM  OR  POWDERY  MILDEW  OP  THE  VINE.  323 

A  mature  perithecium  consists  of  a  nearly  spherical  case  containing 

from  four  to  eight  cell-sacks  called  asci.  The  walls  of  this  case  are 
strong  and  resistant  to  cold  and  other  unfavorable  conditions  which 
destroy  the  summer  forms  of  the  fungus.  They  are  made  up  of  thick 
polygonal  cells  and  form  a  very  efficient  protection  to  the  asci.  An 
ascus  contains  from  four  to  six  spores.     (See  figs.  8  and  5,  IV.) 

Each  perithecium  is  furnished  with  10  to  25  hair-like  appendages 
of  about  the  same  thickness  as  the  mycelial  threads  and  from  one-one 
hundredths  to  one-fiftieth  of  an  inch  in  length.  These  appendages  are 
divided  by  several  cross  partitions  and  are  coiled  at  the  free  end.  They 
consist  usually  of  a  single  thread,  but  occasionally  branch.     (See  fig. 

5,  II.) 

The  perithecia  remain  upon  the  canes  and  leaves  or  in  the  soil  until 
the  return  of  warm  weather  in  spring.  As  soon  as  the  temperature 
becomes  sufficiently  high,  the  walls  of  the  perithecia  break  open  and 
allow  the  asci  to  emit  their  spores.  These  spores,  when  they  reach  a 
leaf  or  growing  shoot,  germinate  in  the  same  manner  as  the  summer 
spores  and  give  rise  to  a  new  generation  of  Oidium. 

The  perithecia  do  not  all  emit  their  spores  at  the  same  time  owing 
to  the  different  conditions  of  the  places  in  which  they  have  passed  the 
winter.  Some  may  even  remain  in  the  soil  until  the  following  spring. 
Perithecia  have  been  shown  to  contain  spores  capable  of  germination 
eighteen  months  after  their  formation.1  It  is  therefore  impossible  to 
completely  exterminate  the  fungus  in  a  vineyard  in  one  year,  however 
thorough  the  treatment.  Burying  the  perithecia  by  plowing-in  simply 
aids  in  their  preservation  and  they  are  ready  to  cause  a  new  infection 
two  years  later  when  brought  to  the  surface  again  by  later  plowing. 
Although  the  Oidium  was  introduced  into  Europe  as  early  as  1845,  it 
was  not  until  1892  that  the  winter  form  of  the  fungus  was  found  there. 
It  was  for  this  reason  uncertain  until  that  time  that  our  Oidium  and 
that  of  Europe  were  identical. 

It  seems  probable  that  the  fungus,  under  some  conditions,  can  pass 
the  winter  in  the  conidial  or  summer  form.  At  all  events,  in  certain 
districts  the  perithecia  have  never  been  found  and  are  therefore  absent 
or  very  rare.  They  are  very  rare  in  the  interior  valleys  of  California. 
On  the  other  hand,  they  are  produced  in  immense  numbers  on  vines 
within  the  influence  of  the  summer  ocean  fogs.  At  Berkeley  it  is  com- 
mon to  find  thousands  of  them  on  every  leaf  and  cane  of  a  vine.  More 
than  100,000  perithecia  have  been  counted  on  the  upper  surface  of  a 


1  Eevue  de  Viticulture,  No.  655,  p.  9. 


324 


UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 


ml 
%  ■ 


♦■■ 


Tf^'*  * 


Fig.  7.  Photomicrograph  of  Perithecia  taken  from  Vine  Leaf;  magnified  30  times. 
The  light  colored  bodies  are  immature  perithecia ;  the  dark  colored,  mature 
perithecia  which  have  been  burst  open  by  pressure. 


Fig.  8.  Photomicrograph  of  Perithecia  magnified  about  200  times.  One  perithe- 
cium  has  been  broken  by  pressure  and  the  asci  are  partially  pressed  out. 
The  winter  spores  can  be  seen  through  the  transparent  walls  of  the  asci. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE.  325 

single  leaf,  arid  as  each  perithecium  contains  fifty  or  more  spores,  the 
number  produced  on  a  single  vine  may  be  hundreds  of  millions. 

In  Europe  they  are  formed  in  September  and  October.  In  Berke- 
ley they  are  found  in  abundance  as  early  as  the  middle  of  June.  Their 
formation  seems  to  depend  on  weather  conditions.  If  after  a  period 
of  warm,  moist  weather,  which  has  produced  an  abundant  growth  of 
mycelium,  the  temperature  suddenly  falls  to  near  the  lowest  limit  for 
the  growth  of  the  fungus  (50°  P.),  they  are  produced  rapidly  and  in 
great  numbers.  These  are  weather  conditions  which  often  occur  at 
Berkeley  and  in  the  valleys  nearest  the  coast. 

In  the  interior  very  different  conditions  exist.  The  fungus  may 
grow  abundantly  during  the  spring  and  early  summer,  but  there  is 
seldom  any  fall  of  temperature  at  this  season  sufficient  to  cause  the 
production  of  the  winter  spores.  As  the  summer  advances,  the  air  be- 
comes too  hot  and  dry  for  the  fungus,  so  that  by  the  time  the  cooler 
weather  of  October  arrives,  most  of  the  Oidium  has  disappeared  and 
the  abundant  growth  of  strong  mycelium  which  is  necessary  does  not 
exist. 

CONDITIONS  FAVOKING  THE  DISEASE. 

Variations  in  Susceptibility  of  Varieties.  There  is  considerable 
difference  in  the  susceptibility  of  various  varieties  of  vines  and  there- 
fore in  the  ease  with  which  they  can  be  kept  fr£e  from  the  disease.  All 
species  of  American  vines, — Labrusca,  Riparia,  Rupestris,  etc., — are 
much  less  severely  attacked  than  the  European  varieties  of  Vitis 
vinifera. 

Among  the  latter  there  exist,  however,  various  degrees  of  suscepti- 
bility. Of  the  varieties  cultivated  in  California,  those  most  easily  and 
severely  attacked  are  the  Carignane.  Flame  Tokay,  Muscat  of  Alex- 
andria, Gutedel,  Cabernet,  Riesling,  Clairette,  Folle  blanche,  Ugni- 
blanc,  and  Petite  Sirah.  The  more  resistant  are  the  Beclan,  Duriff, 
Malbec,  Mataro,  Grenache,  Alicante  Bouschet,  Petit  Bouschet,  Am- 
nion, Mourastel,  Vernaccia,  and  Marsanne.  All  varieties,  however,  are 
capable  of  being  severely  injured  if  the  weather  conditions  favor  the 
growth  of  the  fungus.  The  Beclan  and  Duriff  are  perhaps  the  most 
resistant  of  all  mentioned  and  are  for  this  reason  very  valuable  vari- 
eties to  plant  in  localities  within  the  influence  of  the  summer  ocean 
fogs. 

Temperature  and  Moisture  Conditions.  The  fungus  requires  cer- 
tain degrees  of  temperature  and  moisture  for  its  development.  It 
grows  most  vigorously  and  abundantly  in  sheltered  shady  positions. 


326  UNIVERSITY  OF  CALIFORNIA— EXPERIMENT  STATION. 

For  this  reason,  vines  on  walls  or  trellises  are  more  liable  to  attack, 
while  vines  out  in  the  open  vineyard,  especially  where  they  are  sub- 
jected to  the  full  action  of  the  wind,  are  less  severely  affected. 

Though  the  fungus  requires  less  moisture  than  most  others  causing 
diseases  of  the  vine,  it  will  not  grow  in  an  atmosphere  that  is  too  dry. 
In  the  drier  regions  of  California  it  is  much  less  frequent  than  along 
the  coast.  Vines  in  low  places  or  near  the  banks  of  rivers  or  irrigation 
canals  are  often  attacked  when  the  rest  of  the  vineyard  is  free.  Rains 
or  fogs  in  the  spring  or  early  summer  are  very  favorable  to  the  growth 
of  Oidium,  especially  if  they  are  accompanied  by  a  warm  temperature. 

The  fungus  will  grow  at  a  wide  range  of  temperature.  Below  50° 
F.,  however,  its  growth  is  arrested  and  for  15  or  20  degrees  above  this 
its  growth  is  slow.  Above  75°  F.,  its  growth  is  rapid  and  reaches  its 
maximum  at  about  90°  F.  or  95°  F.,  providing  the  air  remains  suffi- 
ciently moist.  At  about  100°  F.  it  ceases  to  grow  and  at  few  degrees 
above  this  it  is  killed. 

These  considerations  explain  the  different  ways  in  which  the  fungus 
attacks  vines  in  different  localities  and  in  different  seasons. 

In  the  coast  regions,  during  the  spring,  the  Oidium  attacks  most 
severely  the  outer  leaves  and  the  ends  of  shoots  on  the  south  and  east 
sides  of  the  vine.  The  parts  of  the  vine  which  are  shaded  do  not  be- 
come sufficiently  warm  for  the  growth  of  the  fungus.  As  the  season 
progresses  and  the  temperature  of  the  air  rises,  the  west  and  north 
sides  of  the  vine  become  affected  and  finally,  by  midsummer,  the  fun- 
gus is  able  to  grow  on  all  parts  of  the  vine  and  the  bunches  and  bases 
of  the  canes  are  attacked.  Very  near  the  coast  all  parts  of  the  vine  are 
liable  to  attack  throughout  the  summer,  but  in  the  main  coast  valleys,, 
the  fungus  is  usually  confined  to  the  interior  of  the  vine  after  the 
middle  or  end  of  June. 

In  the  interior  valleys,  it  is  very  unusual  to  find  the  outer  leaves  of 
the  vines  attacked  at  any  season.  Vines  which  are  much  shaded  by 
neighboring  trees  or  buildings,  however,  may  be  attacked  in  the  late 
spring  in  a  way  similar  to  that  which  occurs  nearer  the  coast.  Usually 
the  fungus  is  first  seen  at  or  just  before  blossoming  time  and  its  attacks 
are  confined  to  the  canes,  flower  bunches,  and  interior  leaves.  This 
early  attack  sometimes  causes  a  great  loss  of  crop  even  when  to  a  cur- 
sory examination  the  vine  appears  perfectly  healthy. 

During  the  summer,  the  dry  air  and  great  heat  prevent  the  devel- 
opment of  the  fungus,  and  in  fact  destroy  the  greater  part  of  it.  The 
crop,  however,  may  be  seriously  injured  before  sufficiently  hot  weather 
arrives.     Most  varieties  of  grapes  in  the  hotter  parts  of  the  Sacra- 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE.  327 

mento  and  San  Joaquin  valley  will  ripen  their  fruit  perfectly  if  they 
escape  the  spring  infection.  Late  ripening  varieties,  however,  such  as 
some  of  the  table  grapes,  may  be  attacked  during  the  cooler  weather  of 
autumn  and  in  some  seasons  any  variety  growing  vigorously  in  moist 
places  may  be  attacked  during  summer  and  autumn. 

CULTUEAL  METHODS  OF  CONTROL. 

The  Oidium  can  be  checked  to  some  slight  extent  by  cultural  meth- 
ods. Anything  which  permits  the  sun  and  air  to  get  to  all  parts  of 
the  vine  more  completely  will  lessen  the  danger  from  mildew.  Rows 
of  trees  which  shade  the  vines  on  the  south  side  can  often  be  removed 
with  advantage.  Vines  planted  wide  apart  are  less  subject  to  the  dis- 
ease, as  they  dry  off  more  quickly  in  the  morning.  For  the  same  reason^ 
the  rows  of  trellised  vines  should  run  north  and  south  in  order  to  facil- 
itate the  drying  action  of  the  rising  sun.  Low  trellised  vines  are  often 
less  subject  to  Oidium  than  ordinary  vines,  as  the  foliage  is  spread 
over  a  larger  surface  and  not  massed  around  the  head  as  in  vase  prun- 
ing. On  the  other  hand,  high  trellised  vines  are  usually  more  subject, 
as  the  wind  and  sun  do  not  penetrate  them  so  well. 

Drainage  of  the  wet  places  in  a  vineyard  and  methods  of  pruning 
and  training  which  spread  the  vine  out  so  that  no  part  is  surrounded 
by  still  moist  air  will  tend  to  diminish  the  intensity  of  the  disease. 

SULFUR  TREATMENT. 

Mode  of  Action.  No  cultural  method  is  capable  of  completely  pro- 
tecting the  vines  from  Oidium  except  under  the  most  favorable  condi- 
tions and  with  the  most  resistant  varieties.  Some  special  treatment 
therefore,  is  nearly  always  necessary.  Of  all  the  methods  tried,  there 
is  none  so  effective  as  the  dusting  of  powdered  sulfur  over  the  vines. 

Sulfur  acts  by  means  of  the  fumes  it  gives  off  when  the  tempera- 
ture is  sufficiently  high.  These  fumes  destroy  the  mycelium  and 
summer  spores  of  the  fungus,  and  if  present  in  sufficient  abundance 
will  destroy  every  vestige  of  Oidium  in  the  vineyard  with  the  exception 
of  the  perithecia. 

The  exact  nature  of  the  fumes  given  off  is  uncertain.  Some  authors 
believe  them  to  consist  of  sulfurous  acid  gas  identical  with  that  pro- 
duced by  the  burning  of  sulfur  and  to  be  due  to  slow  oxidation.  The 
odor  perceptible  on  a  hot  day  in  a  sulfured  vineyard,  however,  has  not 
the  pungent  nature  characteristic  of  the  fumes  of  burning  sulfur,  but 
resembles  that  of  hydrogen  sulfid,  which  other  authors  believe  to  be 


328  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 

the  active  substance.  Other  investigators  claim  that  the  active  fumes 
are  simply  vapors  of  pure  sulfur  volatilized  by  the  high  temperature. 

The  active  fumes,  whatever  their  nature,  are  given  off  in  effective 
quantities  only  after  the  temperature  of  the  air  reaches  about  75°  F. 
Above  this  point  they  are  given  off  the  more  actively  the  higher  the 
temperature.  Below  75°  F.  the  fungus  grows  very  slowly  and  the 
sulfur  fumes  are  little  needed,  and,  as  the  air  warms  up  to  a  temper- 
ature at  which  the  fungus  grows  rapidly,  the  fumes  are  given  off  in 
greater  abundance. 

The  lower  the  temperature  the  more  slowly  the  fungus  is  affected. 
If  the  highest  shade  temperature  of  the  day  is  between  75°  and  80°  F., 
it  will  require  from  seven  to  eight  days  to  destroy  all  the  mycelium. 
When  the  temperature  rises  to  90°-95°  F.,  the  fungus  commences  to 
show  signs  of  injury  in  24  hours  and  in  four  or  five  days  is  destroyed. 
If  the  thermometer  rises  to  above  100°  F.  in  the  hottest  part  of  the 
day,  one  or  two  days  are  sufficient  to  completely  rid  the  vineyard  of 
the  disease. 

In  order  to  obtain  these  perfect  results,  however,  the  sulfur  must 
be  applied  to  every  part  of  the  vine.  The  nearer  a  spore  or  a  piece  of 
mycelium  is  to  a  particle  of  sulfur,  the  more  quickly  it  is  killed.  Ex- 
cept in  the  hottest  weather,  the  sulfur  on  one  leaf  is  almost  without 
effect  on  the  fungus  on  a  neighboring  leaf.  The  utility,  indeed  the 
necessity,  of  a  perfect  distribution  of  the  sulfur,  especially  in  compar- 
atively cool  weather,  is  apparent. 

The  air  is  always  hottest  near  the  soil,  and  sulfur  placed  on  the  soil 
should  give  off  more  abundant  fumes.  Practice  has  shown,  however, 
that  sulfur  placed  in  this  position  has  almost  no  effect  on  the  Oidium 
except  in  extremely  hot  weather.  In  such  weather,  sulfur  is  hardly 
ever  needed  in  California,  as  it  is  usually  accompanied  by  such  a  dry 
condition  of  the  air  that  the  fungus  is  killed  without  the  aid  of  sulfur 
fumes. 

In  exceptional  cases,  as  for  instance  where  very  vigorous  vines  are 
growing  in  very  moist  places  in  the  irrigated  regions  or  when  un- 
usually hot  weather  occurs  in  the  coast  regions,  the  air  may  be  moist 
enough  for  the  growth  of  Oidium  even  when  the  temperature  rises  to 
considerably  above  100°  F.  In  such  cases  it  is  sometimes  desirable  to 
sprinkle  the  sulfur  on  the  ground  instead  of  on  the  vines.  The  reason 
of  this  is  that  if  the  air  is  sufficiently  hot  the  sulfur  may  injure  both 
the  fruit  and  the  leaves  of  the  vines.  The  fruit  and  leaves  may  be 
spotted  and,  in  severe  cases,  may  fall  completely  or  in  part.  Such 
effects  are  to  be  feared,  however,  only  when  the  temperature  exceeds 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE.  329 

110°  F.,  or  with  varieties  particularly  susceptible  to  sulfur  fumes, 
such  as  Isabella,  Othello,  and  certain  other  American  varieties  and 
hybrids. 

If  the  earlier  snlfu  rings  are  done  properly,  however,  it  will  seldom 
be  necessary  to  treat  the  vines  in  such  weather  and  we  may  consider 
that  the  sulfur  which  goes  on  the  ground  is  almost  completely  wasted. 

Effects  of  Sulfur  on  the  Vine,  Fruit,  and  Wine.  The  effect  of 
sulfur  on  the  vine  is  in  no  way  injurious  except  under  the  conditions 
already  noted.  On  the  contrar}^  most  observers  concur  in  noting  im- 
provement in  the  health  and  vigor  of  the  vines  after  sulfuring  irre- 
spective of  the  control  of  mildew.  Whether  this  is  due  to  some  stimu- 
lating action  of  the  sulfur  on  the  foliage  or  to  its  action  on  the  plant 
food  in  the  soil  is  in  doubt. 

The  favorable  influence  of  sulfuring  the  vines,  while  in  blossom,  on 
the  setting  of  the  fruit  is  even  more  generally  recognized.  If  Oidium 
is  present,  this  is  easily  accounted  for  by  the  prevention  of  the  action 
of  the  fungus  on  the  blossoms.  The  effect,  however,  is  noticed  even 
when  no  Oidium  exists  in  the  vineyard.  The  tendency  of  many  vari- 
eties to  " couture/ } — dropping  their  blossoms  without  setting, — can  be 
lessened  by  vigorous  sulfuring  during  the  blossoming  period.  Whether 
this  is  due  to  a  stimulation  of  the  floral  organs  under  the  action  of  the 
sulfur,  to  the  destruction  of  unrecognized  fungi  on  the  blossoms,  or 
merely  to  the  mechanical  action  of  the  current  of  air  produced  by  the 
blowers  in  promoting  pollination  has  never  been  determined. 

Heavy,  late  sulfuring  may  introduce  notable  quantities  of  sulfur 
into  the  wine.  This  sulfur  is  apt,  under  the  influence  of  the  yeast,  to 
give  a  disagreeable  odor  of  sulfureted  hydrogen  to  the  wine.  This 
odor  is  usually  temporary  and  disappears  after  a  few  rackings  of  the 
wine.  When  the  sulfuring  is  done  with  a  suitable  machine,  however, 
so  little  sulfur  is  placed  upon  the  grapes  that  this  danger  is  not  to  be 
feared. 

Properly  sulfured  vines  ripen  their  grapes  from  7  to  10  days  earlier 
than  those  attacked  by  Oidium.  This  is  probably  due  to  the  better 
health  of  the  vines,  which  allows  the  fruit  to  develop  more  quickly  and 
more  perfectly. 

Proper  time  and  Weather  for  Sulfuring.  The  time  of  day  at  which 
the  sulfur  is  applied  is  of  little  importance,  provided  the  weather  is 
suitable.  It  may  be  applied  when  the  leaves  are  dry  or  when  they  are 
moist  with  dew.  It  is  less  effective,  however,  if  the  leaves  are  very  wet, 
as  the  drops  of  water  have  a  tendency  to  gather  the  sulfur  into  patches 
and  leave  parts  of  the  leaf  untreated. 


330  UNIVERSITY  OP  CALIFORNIA EXPERIMENT   STATION. 

It  is  impossible  to  do  the  work  perfectly  in  a  high  wind,  but  a 
gentle  breeze  is  an  aid  in  making  the  sulfur  penetrate  to  all  parts  of 
the  vine. 

Rain  or  very  heavy  and  continued  winds  following  immediately 
after  the  sulfuring  will  remove  most  of  the  sulfur  before  it  has  pro- 
duced the  desired  effect  on  the  fungus,  and  the  treatment  must  be  re- 
peated. Each  sulfuring  should  be  followed  by  from  one  to  four  days 
of  warm  weather  before  the  sulfur  is  removed  by  rain  or  wind.  One 
or  two  days  at  or  about  90°  F.  to  95°  F.,  maximum  shade  temperature, 
or  four  or  five  days  between  85°  F.  and  90°  F.  will  usually  give  satis- 
factory results.  If  rain  comes  before  the  sulfur  has  been  subjected  to 
such  temperature,  the  vines  must  be  resulfured. 

As  already  noted,  sulfuring  in  excessively  hot  weather  should  be 
avoided  on  account  of  the  danger  of  burning  grapes  or  foliage.  For 
the  same  reason,  any  cultivation  or  other  disturbance  of  the  vines 
should  be  avoided  in  hot  weather  immediately  following  the  application 
of  sulfur. 

Proper  Season  for  Sulfuring.  The  proper  season  for  sulfuring  will 
depend  on  the  number  of  sulfurings  needed.  This  number  will  differ 
according  to  locality,  weather,  variety,  and  the  exposure  of  the  vine- 
yard and  will  vary  from  one  to  three  in  the  interior  valleys  to  from 
two  to  five  in  the  coast  valleys,  or  even  as  high  as  six  or  seven  with 
susceptible  varieties,  in  bad  seasons  in  close  proximity  of  the  coast. 

The  most  necessary  and  effective  sulfuring  of  all,  and  one  which 
should  never  be  omitted  under  any  conditions,  is  at  the  time  when  the 
vines  begin  to  open  their  blossoms.  Even  with  the  most  resistant  vari- 
eties, in  the  least  affected  districts,  this  sulfuring  should  be  applied. 
Even  where  there  is  little  or  no  danger  of  Oidium,  the  gain  in  better 
setting  of  the  fruit  has  been  so  frequently  demonstrated  that  it  amply 
repays  the  outlay.  As  all  varieties  do  not  blossom  at  the  same  time,  the 
mixing  of  varieties  in  the  same  block  should  be  avoided,  for  this  and 
other  reasons. 

Number  of  Treatments.  In  the  interior,  if  this  sulfuring  were  reg- 
ularly and  universally  applied,  it  would  usually  be  sufficient.  As  many 
growers  totally  neglect  sulfuring,  however,  there  is  danger  of  reinfec- 
tion from  neighboring  vineyards  during  the  early  summer.  The  vines 
should  be  watched,  therefore,  and  upon  the  first  signs  of  Oidium,  a 
second  sulfuring  should  be  applied.  This  will  usually  be  at  the  time 
the  grapes  are  about  the  size  of  buckshot.  Later  than  this  there  is 
little  danger  usually,  as  the  air  becomes  too  hot  and  dry  for  the  growth 
of  the  fungus.    The  vines  should  be  watched,  however,  especially  those: 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE.  331 

in  moist  parts  of  the  vineyard — near  irrigation  ditches  or  in  the  shade 
of  trees.  Very  vigorous  vines  or  susceptible  varieties  in  cool  seasons 
also  may  exceptionally  require  another  sulfuring  jnst  before  the  grapes 
commence  to  color  or  to  soften.  These  late  sulfurings,  however,  are 
dangerous  in  the  hot  districts  for  reasons  already  given,  and  can  nearly 
always  be  avoided  if  the  earlier  treatments  are  applied  properly  and  in 
time. 

There  are  cases  where  it  is  advisable  even  in  the  interior  to  give  the 
vines  a  sulfuring  before  the  blossoming  time.  If  the  vines  were  badly 
attacked  during  the  previous  season  there  will  be  an  abundance  of 
spores  in  the  vineyard  and  much  injury  may  be  done  before  the  blos- 
soming time  if  the  spring  is  warm.  In  such  cases,  it  is  best  to  give  an 
early  sulfuring  at  the  time  the  vine  shoots  are  about  6  to  8  inches  long. 
For  this  sulfuring  it  is  very  necessary  to  choose  suitable  weather.  If 
unfortunately  this  treatment  is  followed  by  rain  or  continued  heavy 
winds  without  any  intervening  warm  days,  it  should  be  repeated. 

This  early  sulfuring  is  very  useful  also  in  destroying  the  mites 
causing  erinose,1  a  disease  which  often  does  considerable  damage  to  the 
vines  before  the  weather  is  warm  enough  for  very  rapid  growth  of 
Oidium.  The  erinose  attacks  with  particular  intensity  Mission  and 
Flame  Tokay. 

In  the  coast  valleys,- — Sonoma,  Napa,  Santa  Clara,  etc., — two  sul- 
furings should  always  be  given ;  the  first  at  the  time  the  shoots  are 
from  6  to  8  inches  long.  This  treatment  might  be  omitted  in  dry,  well 
ventilated  situations  with  resistant  varieties,  if  sulfuring  were  univer- 
sally practised  throughout  the  district,  but  it  is  at  present  always  safer 
to  apply  it.  The  second  sulfuring  should  be  at  blossoming  time.  In 
dry  early  summers,  except  with  the  most  susceptible  varieties  such  as 
Carignane,  a  third  sulfuring  will  often  be  unnecessary.  The  vine 
should  be  carefully  watched,  however,  and,  on  the  first  appearance  of 
mildew,  sulfur  applied  again.  In  bad  seasons  a  fourth  sulfuring  just 
before  the  commencement  of  ripening  may  be  necessary.  By  watching 
the  parts  of  the  vineyard  which  experience  has  shown  to  be  the  most 
quickly  affected,  it  is  always  possible  to  control  the  disease  before  it 
has  done  any  serious  damage. 

After  the  grapes  have  commenced  to  ripen,  they  are  almost  safe 
from  the  attacks  of  Oidium,  but  it  is  a  mistake  for  this  reason  to  allow 
the  fungus  to  become  abundant  on  the  leaves,  as  it  may  in  warm,  moist 
autumns.    Though  such  a  late  attack  may  do  little  or  no  damage  to  the 


1  See  Bulletin  No.  136,  "The  Erinose  of  the  Vine." 


332  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 

current  crop,  it  will  injure  the  buds  and  canes  on  which  the  crop  of 
the  following'  year  depends.  Moreover,  it  is  this  late  growth  of  mildew 
which  produces  the  winter  spores  and  promotes  an  early  and  severe 
attack  of  the  disease  during  the  following  spring.  The  vines  therefore 
should  be  kept  free  from  Oidinm  even  if  it  requires  a  sulfuring  after 
the  grapes  are  gathered. 

In  the  coast  districts  where  weather  conditions  similar  to  those  of 
Berkeley  exist,  even  three  sulfurings  will  seldom  be  sufficient  to  hold 
the  Oidium  completely  in  check.  Where  the  springs  are  warm  and  the 
summers  comparatively  cool  and  moist,  as  along  the  coast  of  Santa 
Cruz,  the  fungus  finds  conditions  favorable  to  its  development  at  all 
times  of  the  year  when  the  vines  are  in  leaf.  In  such  locations  an  early 
sulfuring,  when  the  shoots  are  3  or  4  inches  long,  another  at  blossoming 
and  a  third  when  the  grapes  are  the  size  of  buckshot  are  always  neces- 
sary. If  these  are  thorough  and  there  are  no  neighboring  neglected 
vineyards  to  spread  continuous  reinfection,  certain  varieties  may  be 
kept  free  in  good  years  by  three  sulfurings.  It  will,  however,  usually 
be  necessary  to  interpolate  another  treatment  between  the  first  and 

that  at  blossoming  time  and  follow  the  third  with  one  or  two  supple- 

k 
mentary  treatments. 

Sulfuring  Young  Vines.  Young  vines,  whether  in  the  vineyard  or 
the  nursery,  should  not  be  neglected.  In  the  nursery  they  are  pecu- 
liarly susceptible  owing  to  their  nearness  to  each  other  and  to  the  moist 
air  near  the  irrigated  soil.  Autumn  sulfuring  is  nearly  always  useful 
in  this  case  to  keep  the  leaves  healthy  until  they  have  ripened  the  canes. 
Young  vines  during  the  first  year  in  the  vineyard  are  seldom  seriously 
injured  by  mildeAv,  but  it  is  advisable  to  sulfur  them  at  least  once  dur- 
ing the  early  summer. 

Methods  of  Applying  Sulfur.  From  what  has  been  said  of  the 
action  of  sulfur  on  the  fungus,  it  is  clear  that  thorough  distribution  is 
the  main  factor  in  its  effective  application.  Providing  we  get  some 
sulfur  on  every  part  of  every  vine  in  the  vineyard,  the  amount  we  use 
is  of  little  importance  in  controlling  the  disease. 

Whatever  the  fumes  may  be  which  are  given  off,  the  amount  of 
sulfur  used  in  producing  them  is  infinitesimal.  The  smallest  quantity 
of  sulfur  we  can  possibly  use  in  practice  is  amply  sufficient  if  we  ac- 
complish the  object  of  leaving  no  part  of  the  vine  untouched. 

On  a  properly  sulfured  vine  the  distribution  is  so  perfect  that  on 
close  examination  we  are  unable  to  find  a  square  inch  of  surface  free 
from  sulfur  grains.  On  the  other  hand,  if  on  looking  at  a  vine  from 
a  distance  of  twenty  feet  we  can  see  any  signs  of  the  sulfur  applied, 
more  than  enough  has  been  used. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE.  333 

If  the  distribution  is  defective,  we  not  only  fail  to  free  all  parts  of 
the  vine  from  the  Oidium  but  we  leave  enough  of  the  fungus  to  spread 
rapidly  through  the  vineyard  as  soon  as  the  sulfur  has  been  removed 
by  rain  or  wind.  Two  or  three  incomplete  sulfurings  which  fail  to 
reach  a  number  of  whole  vines  or  parts  of  vines  are  often  less  effective 
than  one  thorough  treatment  which  leaves  no  part  of  any  vine  un- 
touched. 

The  methods  used  in  California  for  sulfuring  vines  are  the  fol- 
lowing : 

1.  Throwing  the  sulfur  on  the  vines  by  hand ; 

2.  Distributing  by  perforated  cans  of  various  forms ; 

3.  Shaking  through  the  tissue  of  a  cloth  sack  ; 

4.  Various  forms  of  hand  bellows ; 

5.  Various  forms  of  knapsack  bellows ; 

6.  Traction  sulfur  distributers. 

The  disease  can  be  completely  controlled  by  any  of  these  methods. 
They  differ  only  in  the  amount  of  labor,  sulfur,  and  care  necessary  in 
applying  them.    In  these  respects,  however,  they  differ  very  notably. 

1.  Throwing  on  by  hand  is  undoubtedly  the  most  laborious,  dis- 
agreeable, and  wasteful.  Something  like  90  per  cent,  or  more  of  the 
sulfur  is  wasted  because  most  of  it  goes  on  the  ground,  and  of  that 
which  goes  on  the  vine  a  few  leaves  usually  receive  the  bulk.  When 
the  vines  are  large,  if  all  parts  of  the  vine,  extremities  of  canes  and 
center  of  head,  are  properly  treated,  from  five  to  twenty  times  as  much 
sulfur  will  be  used  as  by  the  best  methods.  It  also  requires  more  time 
than  the  better  methods.  It  is  moreover  very  difficult  to  get  men  to 
sulfur  effectively  by  this  means  owing  to  the  large  amount  of  sulfur 
they  get  into  their  eyes  and  mouths.  They  are  naturally  apt  to  think 
more  of  protecting  themselves  than  of  destroying  the  mildew. 

2.  Distribution  from  perforated  cans  is  perhaps  the  commonest 
method  of  application.  It  is  a  little  better  than  hand  throwing,  but 
wastes  a  great  deal  of  sulfur.  With  large  vines  from  five  to  ten  times 
as  much  is  used  as  is  necessary.  It  is  very  difficult  to  reach  the  tops  of 
high  vines  with  the  ordinary  forms  of  cans.  Some  sulfur  cans  are 
made  with  a  long  handle,  which  obviate  this  defect  to  some  extent  but 
increase  the  difficulty  of  sulfuring  the  low  parts  and  center  of  the  vine. 

In  both  these  methods  it  is  unnecessary  to  use  the  best  brands  of 
sulfur,  as  with  complete  distribution  so  much  is  used  that  there  is 
always  enough  fine  material,  except  with  the  worst  grades,  to  do  the 
work.  Some  growers  mix  the  sulfur  with  lime,  ashes,  road  dust,  or 
some  inert  powder  to  save  sulfur.  The  main  objection  to  this  is  that 
it  involves  the  carrying  and  distribution  of  useless  material. 


334  UNIVERSITY  OP1  CALIFORNIA EXPERIMENT  STATION. 

3.  An  improvement  on  the  last  method  is  the  "use  of  a  sack  from 
which  to  shake  the  snlfnr  on  to  the  vine.  This  sack  should  be  made  of 
cloth  whose  texture  is  close  enough  to  permit  only  fine  particles  of 
sulfur  to  pass,  but  not  so  close  as  to  require  too  much  labor  in  shaking 
out  the  required  amount.  A  sack  about  14  inches  long  and  5  inches  in 
diameter,  holding  about  3  pounds  of  sulfur  when  half  full,  is  a  con- 
venient size.  Somewhat  tightly  woven  grain  sacks  of  good  quality  are 
suitable  material  from  which  to  make  them. 

Very  good  work  can  be  done  with  sacks  of  this  kind  while  the  vines 
are  small.  Their  main  defects  are  that  they  hold  very  little  and  much 
time  is  wasted  walking  to  the  sulfur  supply  to  fill  them.  They  wear 
out  very  quickly  and  the  work  with  them  is  laborious.  They  cannot  be 
used  while  the  vines  are  wet,  as  moisture  on  the  sacks  prevents  the 
sulfur  from  coming  out. 

For  large  and  high  vines  they  are  even  less  suitable  than  the  cans. 
It  is  almost  impossible  to  sulfur  any  part  of  a  vine  higher  than  the 
workman's  head. 

4.  The  use  of  small  hand  bellows  similar  to  that  shown  in  fig.  9,  b 
is  a  great  improvement  over  the  three  methods  just  described.  The 
distribution  of  the  sulfur  is  much  better,  the  workman  less  troubled  by 
the  sulfur,  and  every  part  of  the  vine  can  be  reached. 

The  main  defects  of  these  bellows  are  that  they  are  very  tiring  to 
the  hands  and  arms,  and  as  they  hold  little  sulfur  much  time  is  wasted 
in  filling  them.  While  not  so  wasteful  of  sulfur  as  the  above  methods, 
they  use  more  sulfur  than  is  necessary. 

5.  The  best  knapsack  bellows  are  a  great  improvement  on  the  hand 
bellows.  These  machines  are  known  as  "dust  sprayers,"  "sulfuring 
machines,"  etc. 

There  are  several  hand  "dust  sprayers"  of  American  manufacture 
which  were  originally  designed  for  the  distribution  of  paris  green. 
The  current  of  air  by  which  the  powder  is  blown  on  to  the  plant  is  pro- 
duced by  a  rotary  fan.  The  powder  is  stirred  by  various  devices  in 
the  different  machines  and  blown  out  of  a  reservoir  through  a  tin  or 
rubber  tube. 

The  machines  made  in  Europe  specially  for  the  distribution  of 
sulfur  differ  from  the  above  principally  in  the  method  of  producing 
the  current  of  air.  This  is  produced  by  a  valve  bellows  similar  in  prin- 
ciple to  the  old-fashioned  blacksmith's  bellows. 

All  the  available  American  machines  and  one  of  the  best  European 
machines  were  tested  this  year  by  the  Experiment  Station.  None  of 
the  American  machines  was  found  suitable  for  the  purpose.    They  were 


OIDTUM  OR  POWDERY  MILDEW  OP  THE  VINE. 


335 


Fig.  9.     Various  forms  of  Hand  Sulfur  Distributers. 

a,  Upper  left  hand,  European  machine,     b,  Upper  right  hand,  sulfur  bellows,     c 
and  d,  Lower  figures,  American  machines. 


nearly  all  extremely  cumbersome  and  wasteful  of  sulfur.  The  best  of 
those  tested  is  shown  by  the  photograph  of  fig.  9,  d.  They  all  have 
several  very  serious  defects  for  the  purpose  tested.  The  regulation  of 
the  flow  of  sulfur  is  very  imperfect  and  it  is  necessary  to  use  an  unnec- 


336 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT   STATION. 


essarily  large  quantity  in  order  to  cover  the  whole  vine.  This  is  espe- 
cially true  in  the  case  of  high  vines.  The  machines  worked  fairly  well 
only  when  the  outlet  tube  was  held  in  a  downward  direction.  While 
treating  the  tops  of  high  vines  the  sulfur  accumulates  in  the  tube, 
which  finally  chokes  up.  In  order  to  clear  the  tube  it  is  necessary  to 
hold  it  down,  upon  which  the  accumulated  sulfur  runs  out  and  is 
wasted  on  the  ground. 

The  European  machine,  on  the  contrary,  gave  most  excellent  results. 
(See  fig.  9, a.)  The  regulation  device  enables  the  operator  to  govern 
the  amount  of  sulfur  blown  out  with  great  precision.     This  is  a  very 


Fig.  10.     Sulfur  cloud  to  cover  the  whole  vine. 


important  point,  as  it  makes  it  possible  to  use  various  grades  of  sulfur 
effectively  and  economically.  The  reservoir  of  the  machine  holds 
enough  sulfur  to  treat  two  or  three  acres  without  refilling,  but  is  less 
fatiguing  to  carry  than  the  other  machines,  which  hold  only  one- 
quarter  as  much.  The  sulfur  is  blown  out  in  a  fine  impalpable  powder 
(see  figs.  10,  11,  and  12),  and  owing  to  the  form  of  the  machine  it  can 
be  applied  to  any  part  of  the  vine.  By  standing  a  little  distance  from 
the  vine  a  single  puff  can  be  made  to  distribute  the  sulfur  over  the 
whole  exterior  of  the  vine.     (See  fig.  10.)     Then  after  poking  the  end 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE. 


337 


of  the  tube  into  the  center  of  the  vine  another  puff  will  thoroughly 
sulfur  the  interior.  (See  fig.  11.)  By  a  small  attachment  placed  on 
the  end  of  the  tube  the  cloud  may  be  forced  upwards  and  the  under 
side  of  the  leaves  more  thoroughly  treated  (see  fig.  12),  but  this  is 
seldom  necessary.  The  work  is  much  less  laborious  than  with  any  of 
the  other  methods  tried  and  the  workman  is  less  liable  to  be  troubled 
by  the  sulfur  getting  into  his  eyes. 


Fig.  11.     Sulfuring  interior  of  the  vine. 


Fig.  12.     Sulfuring  the  under  side  of  leaves. 


A  machine  made  in  San  Francisco  on  the  plan  of  the  European 
machines  was  found  excellent  in  all  respects  except  that  it  lacked  the 
regulating  device. 

The  following  table  shows  some  of  the  results  obtained  with  the 
various  methods  of  sulfuring : 


338  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 

SULFUR  AND  TIME  TAKEN  TO  SULFUR  500  VINES  (1  ACRE). 


Meth 

a          2  year  old  Vines 

lbs.  of  S.     time:  in  in. 

3  year  old  Vines 
lbs.  of  S.     time:  min. 

4  year 
lbs.  of  S. 

old  Vines 
time:  min 

A 

4.82 

30 

8.4 

56 

B 

8.61 

30 

11.1 

63 

C 

6.56 

33 

12.7 

56 

D 

9.84 

30 

23.9 

65 

E 

9.43 

33 

28.6 

60 

F 

6.56 

33 

28.9 

58 

G 

12.30 

30 

42.8 

69 

A. 

European  knapsack  bell 

ows. 

(Fig.  9; 

a.) 

B. 

San  Francisco 

knapsack  bellows. 

C. 

Hand  bellows. 

(Fig.  9, 

6.) 

1). 

American  dust 

sprayer 

(the 

best  of  those  tested). 

(Fig.  9,  a. 

) 

E. 

Sulfur  sack. 

F. 

Perforated  car 

i. 

G. 

Hand  distribution. 

Each  of  the  results  given  in  the  above  table  is  the  average  of  four 
tests  made  by  four  men  and  may  be  accepted  as  accurate  so  far  as  the 
amounts  of  sulfur  are  concerned.  The  time  given  for  sulfuring,  how- 
ever, is  less  accurate.  The  four  men  doing  the  sulfuring  worked  to- 
gether with  different  machines,  so  there  was  a  tendency  for  the  man 
with  the  most  laborious  machine  to  work  harder  to  keep  up  with  the 
others.  This  makes  the  difference  in  time  between  the  various  methods 
less  than  it  would  be  in  practice.  No  account,  moreover,  was  taken  of 
the  time  needed  to  go  for  sulfur  and  to  fill  the  machines.  This  would 
still  further  increase  the  differences  in  time. 

In  all  the  tests  made,  the  vines  were  given  as  complete  a  sulfuring 
as  was  possible  with  the  means  employed.  A  fair  sample  of  sublimed 
sulfur  was  used. 

ESTIMATE  OF  COST  OF  SULFURING  500  MATURE  VINES. 

,.   , ,  n  -j  1st  S.        2nd  S.        3rd  S.         Total  Cost       Labor  at       Total 

JieTnoa  lbs.  lbs.  lbs.  S.  lbs.  of  S.      $2  per  day       cost 

European  machine  5.0  7.5  10.0  22.5*  .56  .60*  $1.16 

Hand  bellows  7.0  13.0  20.0  40.0f  .80  .60  1.40 

Dust    sprayer    10.0  20.0  30.0  60.0f  $1.20  .60  1.80 

Perforated  can    7.0  30.0  50.0  87.0f  1.74  .60  2.34 

Hand  distribution  12.0  40.0  75.0  127.0f  3.54  .60  4.14 


*  Sulfur  of  good  quality  at  $2.50  per  100  lbs. 

t  Sulfur  of  medium  quality  at  $2  per  100  lbs. 

+  The  time  required  will  vary  from  three-quarters  of  an  hour  to  one  and  one- 
half  hours  per  acre  (500  vines),  according  to  the  size  of  the  vines  and  the  method 
used.  An  average  of  one  acre  an  hour  is  taken  for  the  three  sulfurings  for  all  the 
machines.  In  practice  it  would  probably  be  less  than  this  for  the  best  machines 
and  more  for  the  inferior  methods. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE.  339 

The  above  estimates  are  based  on  the  tests  made, — tests  which 
proved  effective  in  completely  controlling  the  disease.  The  amounts 
indicated  for  an  acre  when  the  European  machine  is  used  are  less  than 
is  recommended  by  the  best  authorities  in  the  south  of  France.  Viala 
in  l*Les  Maladies  de  la  Vigne"  gives  15-30-40  kilos  as  the  amounts  to 
be  used  for  the  three  sulfurings  of  an  hectare.  This  corresponds  to 
about  75  pounds  to  the  acre.  The  vines  in  the  south  of  France,  how- 
ever, are  planted  much  closer  than  ours,  usually  about  1,800  to  the 
acre.  The  amount  for  500  vines  therefore  would  be  a  little  less  than 
our  tests  indicate. 

Cost  of  Treatment.  The  total  cost  for  sulfuring,  including  mate- 
rial and  labor,  will  vary,  if  the  best  hand  machine  is  used,  from  about 
50  cents  per  acre  for  one  treatment  in  the  interior  to  $1.25  for  three 
treatments  in  the  coast  valleys,  or  $2  to  $2.25  for  five  treatments  in  the 
most  affected  localities. 

Power  and  Traction  Machines.  No  machines  of  this  description 
have  been  tested  by  the  Experiment  Station  for  the  sulfuring  of  vines. 
In  Europe  it  is  only  lately  that  they  have  been  used  at  all.  The  diffi- 
culties attending  the  distribution  of  large  quantities  of  sulfur  in  a  fine 
cloud  by  means  of  a  current  of  air  are  very  great.  It  is  claimed  by  the 
manufacturers  of  several  machines  that  these  difficulties  have  been 
overcome,  but  the  machines  are  very  costly. 

Moreover,  it  is  hard  to  conceive  of  a  machine  which  would  do  the 
work  effectively  without  wasting  a  large  part  of  the  sulfur.  When  the 
vines  are  small,  if  the  sulfur  were  thrown  over  a  large  area,  as  much 
would  go  on  the  ground  as  on  the  vines.  As  the  vines  when  they  first 
start  cover  only  from  5  per  cent,  to  10  per  cent,  of  the  area,  the  amount 
of  sulfur  used  by  the  power  machine  would  be  from  ten  to  twenty  times 
times  as  much  as  is  necessarv.    As  the  cost  of  sulfur  and  of  labor  are 

t/ 

epproximately  equal  with  the  best  knapsack  machine,  no  saving  in  cost 
of  labor  would  offset  this  waste  of  sulfur. 

When  the  vines  are  large  it  is  doubtful  whether  any  machine  could 
throw  the  sulfur  as  effectively  into  the  interior  of  the  vine  where  it  is 
most  needed  as  can  be  done  with  the  tube  of  a  knapsack  machine. 

There  is  one  consideration  which  makes  it  seem  possible,  however, 
that  an  effective  power  machine  might  have  its  uses  here.  There  is 
nothing  more  expensive  than  losing  the  crop,  and  a  power  machine 
might  make  it  possible  to  sulfur  a  vineyard  and  save  the  crop  when  it 
was  impossible  to  have  the  work  done  by  hand.  Even  at  an  extra  cost 
of  several  dollars  per  acre  this  of  course  would  be  an  advantage. 

Quality  of  Sulfur.    Any  kind  of  sulfur  in  the  condition  of  a  pow- 


3-40  UNIVERSITY   OF  CALIFORNIA — EXPERIMENT   STATION. 

der  will  control  the  disease  if  used  as  directed.  Coarse  powders,  how- 
ever, must  be  used  in  much  greater  quantities  and  are  more  difficult  to 
apply  properly.  The  absolute  purity  of  the  sulfur  is  of  little  impor- 
tance, provided  there  is  no  large  adulteration  with  inert  and  useless 
substances  such  as  gypsum. 

Many  samples  of  sulfur  were  received  at  the  Experiment  Station 
during  the  past  year  and  examined.  Most  of  these  samples  were  sent 
by  grape  growers.  They  were  all  found  to  be  practically  pure  and 
unmixed.  In  the  important  matter  of  fineness,  however,  they  differed 
widely.  Two  or  three  of  them  were  so  coarse  as  to  be  almost  valueless 
for  sulfuring  vines.  (See  fig.  16,  Sulfur  No.  8.)  A  few  were  very  good 
and  most  of  them  were  passable.  The  prices  quoted  by  the  senders 
were  little  indication  of  the  value  of  the  samples.  Some  of  the  cheapest 
were  of  excellent  quality  for  the  purpose  (see  fig.  15,  Sulfur  No.  16), 
and  some  of  the  most  expensive  were  among  the  worst  (see  fig.  16, 
Sulfur  No.  8).  This  shows  the  need  of  a  careful  examination  before 
purchasing. 

Some  of  the  results  of  our  examinations  are  shown  in  the  following 
table : 

SAMPLES  OF  SULFUR  RECEIVED  AND  EXAMINED  BY  THE  STATION 

IN  1906. 

No.  Price  C 

30  6ti.S         Sublimed,  very  fine,  no  coarse  material. 

2Z  60.8  Sublimed,  very  good,  very  little  coarse  material. 

3  $52.50         60.0         Sublimed,  very  good,  some  coarse  material. 

20  45.00         58.8  Sublimed,  very  good,  some  coarse  material. 
19            70.00         52.0         Sublimed,  good,  but  with  many  large  grains. 

28  41.00         50.8         Sublimed,  good,  but  with  considerable  coarse  material. 

26  50.0         Sublimed,  good,  but  with  considerable  coarse  material. 

15 49.2  Sublimed,  good,  but  with  some  coarse  material. 

24  43.00         48.0         Sublimed,  fair,  about  one-third  of  coarse  material. 

6  55.00         47.6         Sublimed,  fair,  but  some  coarse  angular  material. 

29  60.00         46.0         Sublimed,  fair,  with  considerable  coarse  material. 

13  44.00         45.6         Sublimed,  fair,  with  considerable  coarse  material. 
18 — ..         42.8         Sublimed,  with  much  medium  coarse  material. 

4  55.00         40.0         Sublimed,  with  much  coarse  material. 

16  32.00         51.6         Ground,  good,  with  little  coarse  material. 

31  ,         46.8         Ground,  good,  with  about  one-third  coarse  material. 

23  46.0         Ground,  good,  with  about  one-third  medium  material. 

25  45.00         46.0         Ground,  fair,  about  one-half  fine  material. 

10  30.00         45.6         Ground,  good,  except  for  some  large  particles. 

17  45.6         Ground,  good,  but  considerable  coarse  material. 

5  40.00         45.2         Ground. 

21  45.00         45.0         Ground,  fair,  about  one-half  fine  material. 

27  30.00         44.5         Ground,  fair,  about  one-half  fine  material. 
12          39.6         Ground,  much  coarse  material. 

1  44.00         37.6         Ground,  much  coarse  material. 

7  45.00         37.6         Ground,  fair,  much  coarse  material. 

2  47.50  37.2  Ground,  coarse. 

11  36.0  Ground,  poor,  very  little  fine  material. 

14  34.4  Ground,  very  poor,  hardly  any  fine  material. 

8  47.50  34.0  Ground,  principally  large  particles. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE. 


341 


Fig.   13.     Sublimed  Sulfur  of  very  good  quality.     Sulfur  No.  30. 


Fig.  14.     Sublimed  Sulfur  of  poor  quality.     Sulfur  No.  4. 


U2 


UNIVERSITY  OF  CALIFORNIA— EXPERIMENT  STATION. 


«T         it  *  '**,."'  .  -^  *   -'■  J-JHC      ..mUtr  ' 


Fig.  15.     Ground  Sulfur  of  good  quality.     Sulfur  No.  16. 


Fig.  16.     Ground  Sulfur  of  very  bad  quality.     Sulfur  No.  8. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE. 


343 


The  data  given  are  the  prices  and  the  results  of  the  Chancel  test, 
column  C.  and  of  the  microscopical  examination.  The  Chancel  test  is 
the  determination  of  the  amount  of  settling  that  occurs  when  5  grams 
of  sulfur  are  allowed  to  stand  in  a  cylinder  after  shaking  up  with  25 
cubic  centimeters  of  ether.  The  number  represents  the  percentage  of 
the  height  of  the  cylinder  occupied  by  the  sulfur  after  settling.  It  is 
a  very  convenient  and  quick  method  of  testing  the  fineness  of  the  sul- 
fur.    (See  fig.  17.) 


30  28  4  16  8 

Fig.  17.      Comparative  volumes  of  5  grams  of  different  sulfurs. 

Xo.  30.  Sublimed  Sulfur,  Chancel  No.  66.8  $70.00 

No.  28.  Sublimed  Sulfur,  Chancel  No.  50.8  41.00 

No.     4.  Sublimed  Sulfur,  Chancel  No.  40.0 55.00 

No.  16.  Ground  Sulfur,  Chancel  No.  51.6 32.00 

No.     8.  Ground  Sulfur,  Chancel  No.  38.0 47.50 

The  numbers  corresponding  to  good  commercial  sublimed  sulfur 
are  50  to  70 ;  those  of  the  finest  quality  show  75  to  90.     Powdered  or 


344  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 

ground  sulfur  of  the  best  quality  will  show  from  60  to  70,  and  those  of 
ordinary  quality  43. 1 

All  the  sulfurs  examined,  with  the  exception  of  two  of  the  ground 
samples  (Nos.  8  and  14),  contained  sufficient  fine  material  to  do  effec- 
tive work,  but  the  amount  it  would  be  necessary  to  use  of  the  various 
grades  would  vary  considerably.  If  the  sulfur  is  applied  by  hand  or 
with  perforated  cans,  any  of  the  sulfurs  except  Nos.  14  and  8  would 
probably  be  nearly  equally  good,  and  therefore  the  cheapest  would  be 
best.  If  we  use  several  times  as  much  as  is  needed,  as  we  must  with 
these  methods,  it  matters  little  if  25  per  cent,  or  50  per  cent,  of  the 
sulfur  is  useless. 

When  using  an  effective  sulfur  machine  it  is  possible  to  utilize  the 
superiority  of  the  finer  grades,  and  in  this  case  it  is  undoubtedly  ad- 
visable to  use  the  better  qualities.     (See  figs.  13  and  15.) 

A  few  simple  directions  for  the  examination  of  sulfur  may  be  of 
use  to  the  grower. 

1.  The  finer  the  sulfur  the  more  bulky.  Therefore  if  several  sul- 
furs are  in  sacks  of  equal  weight,  the  largest  sack  will  contain  the 
finest  sulfur.  A  110-pound  sack  of  good  flowers  of  sulfur  is  twice  as 
large  as  a  110-pound  sack  of  very  coarse  ground.  The  difference  in 
bulk  between  equal  weights  of  sulfurs  of  various  qualities  is  shown  in 
fig.  17,  representing  the  Chancel  test. 

2.  The  color  of  sublimed  sulfur  is  a  clear,  bright  yellow.  The 
color  of  ground  sulfur  will  vary  with  the  fineness.  Coarsely  ground 
sulfur  is  almost  of  the  same  color  as  sublimed.  When  finely  ground, 
the  color  becomes  whitish.  The  whiter  a  ground  sulfur,  the  finer  it  is, 
provided  the  color  is  not  due  to  adulterants. 

3.  A  good  sublimed  sulfur  should  feel  as  soft  as  flour  when  rubbed 
with  the  fingers  in  the  palm  of  the  hand.  If  hard  particles  are  felt, 
the  sulfur  is  not  of  the  best  quality.  Ground  sulfur  always  feels  a 
little  gritty,  but  the  hard  particles  should  not  be  large  or  numerous. 

4.  A  very  good  idea  of  the  fineness  of  a  sulfur  can  be  obtained  by 
the  use  of  an  ordinary  good  hand  magnifying  glass  costing  about  $1. 
A  magnification  of  10  or  20  diameters  is  sufficient.  With  a  little  expe- 
rience sublimed  and  ground  sulfur  can  be  distinguished  by  this  means. 
The  particles  of  sublimed  sulfur  are  all  nearly  spherical  with  smooth 
outlines.    Those  of  ground  sulfur  are  irregular  and  with  sharp  edges. 

The  sulfur  is  most  easily  examined  when  spread  on  a  piece  of  glass 
over  a  dark  background.    A  good  way  to  spread  the  sulfur  is  to  place 


1  Viala,  P.,  Les  Maladies  de  la  Vigne,  p.  53. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE.  345 

a  small  pinch  on  the  glass,  wet  it  with  a  few  drops  of  ether,  and  shake. 
This  will  distribute  the  sulfur  in  a  thin  layer  over  the  glass  and  much 
facilitate  the  examination. 

5.  A  test  of  the  purity  may  be  made  by  burning  a  pinch  of  the 
sulfur  on  a  piece  of  white  porcelain — a  broken  plate,  for  example.  To 
make  the  burning  complete,  hold  the  piece  of  plate  over  a  lamp  or  on 
top  of  a  very  hot  stove.  A  pure  sulfur  burns  away  completely,  leaving 
only  a  black  stain  on  the  plate.  Any  dust  or  particles  that  are  left 
indicate  adulteration. 

The  fine  sulfurs  are  superior  in  three  important  respects:  (1) 
They  capable  of  more  perfect  distribution;  (2)  they  offer  a  larger 
surface  to  the  air  and  therefore  give  off  more  fumes;  (3)  they  adhere 
better  to  the  leaves. 

A  pound  of  a  very  fine  sublimed  sulfur  such  as  No.  30  (see  fig.  13), 
the  particles  of  which  measure  .01  mm.  in  diameter,  if  evenly  distrib- 
uted and  none  lost,  would  give  about  15,000  particles  for  every  square 
inch  of  leaf  and  cane  surface  on  an  acre  of  large  vines.  A  pound  of  a 
very  coarse  sulfur  such  as  No.  8  (see  fig.  16),  the  particles  of  which 
have  twenty-five  times  as  large  a  diameter,  would  supply  only  about 
one  particle  for  every  square  inch.  Moreover,  a  much  larger  propor- 
tion of  the  coarse  sulfur  would  be  lost  by  failing  to  adhere  to  the  leaves 
and  falling  on  the  ground.  Perhaps  the  most  important  advantage  of 
the  finest  sulfur  in  this  respect  is  that  the  impalpable  powder  floats  so 
lightly  in  the  air  that  it  reaches  and  adheres  to  the  lower  surfaces  of 
the  leaves  and  canes.  A  finely  powdered  sulfur  such  as  No.  16  (see 
fig'.  15)  would  probably  be  just  as  effective  as  the  sublimed,  for  though 
it  contains  a  certain  proportion  of  coarser  particles,  the  finer  material 
has  not  the  tendency  to  cohere  in  the  groups  of  particles  characteristic 
of  sublimed  sulfur. 

The  quantity  of  fumes  given  off  by  a  sulfur  must  be  about  in  the 
proportion  of  the  extent  of  surface  which  the  particles  present  to  the 
air.  This  surface  is  inversely  proportionate  to  the  diameter  of  the  par- 
ticles. A  pound  of  sulfur,  No.  30  or  No.  16,  would  possess  a  surface 
twenty-five  times  as  great  as  that  of  No.  14,  and  would  therefore  give 
off  fumes  much  more  rapidly  and  in  greater  quantity. 

OTHER  METHODS  OF  TREATMENT. 

Combined  Treatments.  Various  other  substances  and  sprays  have 
been  suggested  and  tried  for  the  control  of  the  Oidium  during  the 
growing  season.  There  are  two  cases  in  which  it  has  seemed  desirable 
to  attempt  to  find  another  method  of  control.    One  of  these  is  where  it 


346  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT   STATION. 

is  necessary  to  treat  for  another  vine  disease  which  cannot  be  con- 
trolled by  sulfur  at  the  same  time.  In  Europe,  where  spraying  with 
copper  solutions  is  necessary  to  protect  the  vines  from  Peronospora, 
Black  Rot,  and  Botrytis,  various  sprays  have  been  tried  with  the  object 
of  controlling  the  Oidium  at  the  same  time.  These  sprays  are  princi- 
pally liquids  containing  Bordeaux  mixture,  copper  sulfate,  or  sulfoste- 
atite  together  with  "wetable''  sulfur.  There  is  considerable  uncer- 
tainty as  to  the  success  of  these  combinations,  and  as  the  diseases  they 
are  intended  to  reach  do  not  exist  in  California  they  are  of  little  in- 
terest to  us. 

The  other  case  is  where  sulfur  has  been  found  ineffective  or  too 
slow  in  its  action.  This  seems  to  be  the  case  in  the  Eastern  States,  and 
may  be  in  certain  parts  of  the  coast  region  of  California  or  perhaps 
exceptionally  in  other  regions  in  abnormal  years. 

Liquid  Sprays.  Dry  sulfur  to  be  effective  requires  warm  weather. 
If  the  weather  is  cool  its  action  is  slow  or  nil.  Certain  sprays  act  im- 
mediately on  the  Oidium  whatever  the  temperature.  It  should  be  re- 
membered, however,  that  the  Oidium  grows  very  slowly  or  not  at  all 
below  temperatures  at  which  sulfur  is  effective.  Cases,  however,  may 
arise  where,  through  neglect  of  proper  sulfuring,  the  vines  may  be 
badly  attacked  by  mildew,  and  owing  to  the  coolness  of  the  weather 
when  the  trouble  is  first  perceived  sulfur  may  act  too  slowly.  In  such 
cases  it  may  be  advisable  to  use  a  quick  acting  spray. 

Such  a  condition  might  occur  in  a  cool  late  spring. 

Another  case  in  which  a  spray  may  be  useful  is  where  the  vines 
have  been  very  badly  affected  the  previous  autumn  and  the  canes  are 
covered  with  winter  spores  and  perhaps  hibernating  mycelium  ready 
to  infect  the  new  shoots  on  the  first  warm  day.  A  spraying  just  as  the 
buds  swell  might  be  of  help  in  such  a  case.1 

Spraying  in  the  summer  should  never  be  necessary,  as  the  heat  is 
sufficient  to  cause  the  sulfur  to  act  quickly.  It  has  been  suggested  that 
late  sulfuring  is  inadvisable  because  it  may  cause  spotting  of  the 
grapes.  If  the  grapes  have  not  commenced  to  ripen  this  will  not  occur 
if  the  sulfur  is  applied  properly,  and  if  they  have  commenced  to  ripen 
they  are  safe  from  the  disease,  and  sulfuring  to  protect  the  vines  should 
be  deferred  until  the  grapes  are  gathered. 

No  sprays,  however,  do  the  work  as  thoroughly  as  sulfur.  A  spray 
only  kills  the  fungus  which  it  actually  touches,  and  the  most  perfect 
spraying  possible  will  leave  some  parts  of  the  vine  untouched.    Where 


1  Tests  of  winter  spraying  by  Pacottet  and  Eavaz  in  France  gave  no  favorable 
results. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE.  347 

a  spray  is  used  it  should  therefore  be  followed  by  an  application  of  dry 
sulfur  to  complete  the  work. 

The  sprays  which  have  been  found  most  effective  for  this  purpose 
are  Bordeaux  mixture,  permanganate  of  potash,  and  alkaline  polysul- 
fids.  Vines  are  not  easily  injured  by  copper  salts,  so  that  a  strong 
Bordeaux  can  be  used.    The  6-4—50  formula  would  be  suitable. 

Permanganate  of  potash  at  the  rate  of  one  pound  to  100  gallons  of 
water  has  been  found  effective.  A  little  chloride  of  potash  or  common 
salt  improves  the  spray  by  increasing  its  adhesive  qualities. 

Liver  of  sulfur  at  the  rate  of  4  pounds  to  100  gallons  of  water  with 
4  pounds  of  soap  has  also  been  used  with  success.  Alkaline  polysulfids 
have  also  been  used  effectively  in  the  same  way.  These  sprays  are  more 
permanent  in  their  effects  than  the  copper  and  permanganate  mixtures 
because  a  small  amount  of  finelv  divided  free  sulfur  is  set  free,  which 
acts  in  the  same  way  as  the  powdered  sulfur  when  applied  in  the  usual 
way.  It  is  very  probable  that  a  weak  lime-salt-sulfur  spray  such  as  is 
in  common  use  on  fruit  trees  would  be  equally  effective. 

WINTER  TREATMENT. 

As  the  fungus  passes  the  winter,  when  it  has  no  green  leaves  to 
grow  on,  in  the  form  of  resting  spores  on  the  canes  and  in  the  soil  and 
perhaps  of  resting  mycelium  under  the  bud  scales,  it  has  been  sug- 
gested that  a  winter  treatment  which  would  destroy  these  hibernating 
forms  would  be  the  best  method  of  control,  or  at  least  that  it  would 
much  simplify  the  summer  treatment. 

The  methods  usually  proposed  are  to  spray  the  vines  after  pruning 
with  the  lime-salt-sulfur  used  for  fruit  trees  or  with  a  2  per  cent,  solu- 
tion of  Milestone.  Others  advise  swabbing  the  vines  at  the  same  time 
with  a  saturated  solution  of  iron  sulfate  (copperas)  acidified  with  1 
per  cent  .of  sulfuric  acid.  To  make  the  treatment  more  thorough,  some 
remove  all  the  dry  bark  of  the  vine  by  means  of  scrapers  before  treat- 
ment. This  is  supposed  to  destroy  all  the  perithecia  on  the  vine.  In 
order  to  prevent  infection  from  the  hibernating  mycelium  under  the 
bud  scales  it  is  further  advised  to  spray  the  vines  with  Bordeaux  mix- 
ture just  as  the  buds  swell  in  the  spring. 

Such  treatments  as  these  are  of  course  very  expensive  and  cost 
more  than  several  sulfurings,  so  that,  unless  they  can  be  proved  to  be 
effective,  they  should  not  be  adopted.  There  is  considerable  evidence 
that  such  treatment  makes  the  vines  more  vigorous  and  healthy,  but 
that  it  has  any  effect  on  controlling  the  Oidium  is  doubtful.  It  seems 
unnecessary,  because  if  we  control  the  Oidium  in  the  summer,  as  we 


348  UNIVERSITY  OP  CALIFORNIA EXPERIMENT   STATION. 

must  do  to  save  our  crop  entirely,  there  will  be  no  winter  spores  formed 
and,  therefore,  no  use  in  spraying  for  them. 

Winter  treatment,  moreover,  cannot  be  completely  effective  because, 
however  well  done,  it  cannot  destroy  all  the  resting  spores,  because 
most  of  them  are  in  the  soil,  and  if  but  a  few  escape,  they  are  capable 
of  infecting  the  whole  vineyard  when  the  weather  conditions  are  favor- 
able. Sulfuring,  therefore,  is  necessary  even  when  winter  spraying  is 
practised. 

There  is  reason  to  believe,  moreover,  that  winter  treatment  is  com- 
pletely ineffective.  Every  other  vine  in  a  small  patch  of  vines  at 
Berkeley  was  treated  last  winter  with  bluestone,  iron  sulfate,  or  Bor- 
deaux mixture.  In  the  spring  just  as  much  mildew  was  found,  on  its 
first  appearance,  on  the  treated  as  on  the  untreated  vines. 

A  still  more  convincing  experiment  is  described  in  the  "Revue  de 
Viticulture,"  No.  655,  page  12.  This  seems  to  prove  as  well  as  a  single 
experiment  can :  First,  that  the  fungus  does  not  pass  the  winter  to 
any  extent  in  the  summer  form  under  the  bud  scales ;  and  second,  that 
the  most  thorough  winter  treatment  is  useless  if  no  winter  spores  are 
formed,  and  completely  ineffective  if  they  are. 

Mr.  Pacottet  says  in  the  article  quoted :  "In  1904  we  observed  that 
the  spring  attack  of  Oidium  occurred  first  precisely  in  those  hothouses 
of  Nanterre  where  perithecia  had  been  found  in  the  autumn  of  the  pre- 
vious year.  The  same  fact  was  observed  in  1905.  This  led  us  to  make 
careful  observations  the  following  year  on  the  manner  and  time  of  the 
appearance  of  the  Oidium. 

"Oidium  appeared  at  the  end  of  March,  1906,  and  only  in  those 
grape  houses,  to  the  number  of  20,  where  the  presence  of  winter  spores 
had  been  noted  in  November  of  the  previous  year.  In  these  houses  the 
fungus  appeared  with  such  intensity  that  nearly  every  leaf  showed 
simultaneously  several  patches. 

"These  observations  acquire  especial  importance  when  considered 
in  connection  with  the  various  hypotheses  which  have  been  advanced 
regarding  the  modes  in  which  the  Oidium  passes  the  winter,  especially 
as  regards  the  hibernating  of  fragments  of  mycelium  (summer  form) 
adhering  to  the  canes  and  capable  of  vegetating  anew  in  the  spring. 

"At  Nanterre  the  disinfection  of  the  vines  is  as  complete  as  it  is 
possible  to  make  it.  After  removing  the  old  bark  they  are  treated  with 
boiling  water  and  swabbed  with  a  30  per  cent,  solution  of  iron  sulfate. 
They  are  then  covered  with  a  paste  of  lime  and  sulfur,.  #  *  *  Be- 
fore the  starting  of  the  buds,  the  walls,  glass,  and  casings  are  disin- 
fected with  strong  washes  and  the  air  with  the  fumes  of  burning 
sulfur." 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE.  349 

Now,  even  with  such  thorough  winter  treatment  as  this,  which  it 
would  be  quite  impracticable  to  apply  in  a  vineyard,  no  apparent  effect 
was  obtained  in  the  control  of  the  spring  infection.  The  spring  infec- 
tion was  due,  therefore,  to  spores  which  were  not  on  any  part  of  the 
vine,  and  from  which  no  kind  of  spraying  or  swabbing  of  the  vine 
would  be  any  protection  whatever. 

Pacottet  concludes,  therefore,  that  practically  all  the  spring  infec- 
tion is  due  to  spores  which  have  passed  the  winter  in  the  soil.  These 
are  the  spores  contained  in  the  perithecia  which  have  dropped  in  the 
autumn  with  the  leaves  on  which  they  are  formed.  His  advice  for  hot- 
house treatment  is  to  gather  all  these  leaves  before  they  fall  and  to  burn 
them. 

This  again  is  impracticable  in  a  vineyard,  and  we  are  forced  again 
to  the  conclusion  that  no  form  of  winter  treatment  is  of  any  use  in  the 
control  of  Oidium  in  vineyards,  and  that  the  only  practicable  method 
is  proper  sulfuring  of  the  vines  in  spring  and  summer.  This  will  pre- 
vent injury  to  the  vines,  and  if  thorough  will  prevent  the  formation  of 
winter  spores. 

SUMMAEY. 

Oidium  is  one  of  the  most  serious  diseases  of  the  vine  and  the  only 
serious  fungus  disease  of  vines  in  California. 

It  is  capable  of  destroying  the  whole  crop  in  most  vineyards  in  bad 
seasons  if  not  controlled. 

Much  more  damage  is  done  to  vines  and  grapes  in  California  than 
is  usually  supposed,  but  the  control  is  much  easier  and  more  certain 
than  in  most  vine-growing  countries. 

The  disease  attacks  leaves,  canes,  and  fruit  during  the  growing 
season. 

It  grows  only  on  the  exterior  green  surfaces  of  the  vine  and  passes 
the  winter  in  the  form  of  resting  spores  in  the  soil. 

Certain  varieties  of  vines  are  very  susceptible  and  others  compara- 
tively resistant. 

Moist  warm  atmosphere  favors  the  growth  of  the  fungus. 

Methods  of  training,  cultivation,  and  irrigation  which  keep  the  vine 
dry  by  thorough  aeration  minimize  the  danger  of  attack. 

Dusting  the  vines  with  sulfur  is  the  cheapest  and  most  efficient 
method  of  control  in  California. 

The  weather  and  the  season  when  the  sulfur  is  applied  are  of  great 
importance. 


350  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 

The  number  of  treatments  will  differ  with  the  locality,  the  season, 
and  the  variety  of  vine. 

Vines  should  be  protected  from  late  attacks  even  after  the  grapes 
are  gathered. 

Young  vines  should  be  protected  as  much  as  old,  even  when  they 
are  in  the  nursery. 

The  usual  methods  of  applying  sulfur  by  hand  or  with  perforated 
cans  is  wasteful  and  uncertain. 

A  good  sulfur  sprayer  is  essential  for  the  best  results.  None  of  the 
American  dust  sprayers  tried  is  suitable  for  the  purpose.  The  "Ver- 
morel  souf reuse  Torpille"  was  found  to  answer  perfectly. 

The  cost  of  treatment,  when  a  good  sulfur  distributer  is  used,  va- 
ries from  50  cents  to  $2.25  per  acre,  according  to  the  number  of  treat- 
ments necessary.  The  cost  is  about  equally  divided  between  sulfur 
and  labor. 

Traction  machines  do  not  promise  any  improvement  in  cost  or 
efficiency. 

Finely  divided  sublimed  or  powdered  sulfur  should  be  used. 
Coarse  sulfurs  cost  more  because  more  is  needed  and  they  are  less 
effective. 

No  other  form  of  summer  treatment  is  so  effective  as  sulfuring,  but 
in  rare,  special  cases  a  supplementary  spray  may  be  useful. 

Winter  treatment  is  in  all  probability  of  no  use  in  the  control  of 
Oidium. 


OIDIUM  OR  POWDERY  MILDEW  OF  THE  VINE.  351 


STATION  PUBLICATIONS  AVAILABLE  FOR  DISTRIBUTION. 


KEPORTS. 


1896.  Report  of  the  Viticultural  Work  during  the  seasons  1887-93,  with  data  re- 

garding the  Vintages  of  1894-95. 

1897.  Resistant  Vines,  their  Selection,   Adaptation,  and  Grafting.     Appendix  to 

Viticultural  Report  for  1896. 

1898.  Partial  Report  of  Work  of  Agricultural  Experiment  Station  for  the  years 

1895-96  and  1896-97. 
1900.     Report  of  the  Agricultural  Experiment  Station  for  the  year  1897-98. 

1902.  Report  of  the  Agricultural  Experiment  Station  for  1898-1901. 

1903.  Report  of  the  Agricultural  Experiment  Station  for  1901-03. 

1904.  Twenty-second  Report  of  the  Agricultural  Experiment  Station  for  1903-04. 

TECHNICAL  BULLETINS— ENTOMOLOGICAL  SERIES. 

Vol.  1,  No.  1.     Wing  Veins  of  Insects. 

No.  2.     Catalogue  of  the  Ephydridae. 

BULLETINS. 

Reprint.  Endurance  of  Drought  in  Soils  of  the  Arid  Region. 

No.  128.  Nature,  Value,  and  Utilization  of  Alkali  Lands,  and  Tolerance  of  Alkali. 
(Revised  and  Reprint,  1905.) 

133.  Tolerance  of  Alkali  by  Various  Cultures. 

140.  Lands  of  the  Colorado  Delta  in  Salton  Basin,  and  Supplement. 

141.  Deciduous  Fruits  at  Paso  Robles. 

142.  Grasshoppers  in  California.  ; 
144.  The  Peach-Worm.                                                                                              i 

147.  Culture  Work  of  the  Sub-stations. 

148.  Resistant  Vines  and  their  Hybrids. 

149.  California  Sugar  Industry.  ; 

150.  The  Value  of  Oak  Leaves  for  Forage. 

151.  Arsenical  Insecticides. 

152.  Fumigation  Dosage. 

153.  Spraying  with  Distillates. 

154.  Sulfur  Sprays  for  Red  Spider.  .    ■ 
156.  Fowl  Cholera. 

158.  California  Olive  Oil;  its  Manufacture. 

159.  Contribution  to  the  Study  of  Fermentation. 

160.  The  Hop  Aphis. 

161.  Tuberculosis  in  Fowls.     (Reprint.) 

162.  Commercial  Fertilizers.     (Dec.  1,  1904.) 

163.  Pear  Scab. 


352  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 

164.  Poultry  Feeding  and  Proprietary  Foods.     (Keprint.) 

165.  Asparagus  and  Asparagus  Knst  in  California. 

166.  Spraying  for  Scale  Insects. 

167.  Manufacture  of  Dry  Wines  in  Hot  Countries. 

168.  Observations  on  Some  Vine  Diseases  in  Sonoma  County. 

169.  Tolerance  of  the  Sugar  Beet  for  Alkali. 

170.  Studies  in  Grasshopper  Control. 

171.  Commercial  Fertilizers.     (June  30,  1905.) 

172.  Further  Experience  in  Asparagus  Bust  Control. 

173.  Commercial  Fertilizers.     (December,  1905.) 

174.  A  New  Wine-Cooling  Machine. 

175.  Tomato  Diseases  in  California. 

176.  Sugar  Beets  in  the  San  Joaquin  Valley. 

177.  A  New  Method  of  Making  Dry  Bed  Wine. 

178.  Mosquito  Control. 

179.  Commercial  Fertilizers.     (June,  1906.) 

180.  Besistant  Vineyards. 

181.  The  Selection  of  Seed-Wheat. 

182.  Analyses  of  Paris  Green  and  Lead  Arsenate.    Proposed  Insecticide  Law. 

183.  The  California  Tussock  Moth. 

184.  Beport  of  the  Plant  Pathologist. 

185.  Beport  of  Progress  in  Cereal  Investigations. 

Circulars. 

No.      1.  Texas  Fever. 

2.  Blackleg. 

3.  Hog  Cholera. 

4.  Antnrax. 

5.  Contagious  Abortion  in  Cows. 
7.  Bemedies  for  Insects. 

9.  Asparagus  Bust. 

10.  Beading  Course  in  Economic  Entomology.     (Bevision.) 

11.  Fumigation  Practice. 

12.  Silk  Culture. 

13.  The  Culture  of  the  Sugar  Beet. 

15.  Beeent  Problems  in  Agriculture.     What  a  University  Farm  is  For. 

16.  Notes  on  Seed- Wheat. 

17.  Why  Agriculture  Should  be  Taught  in  the  Public  Schools. 

18.  Caterpillars  on  Oaks. 

19.  Disinfection  of  Stables. 

20.  Beading  Course  in  Irrigation. 

21.  The  Advancement  of  Agricultural  Education. 

22.  Defecation  of  Must  for  White  Wine. 

23.  Pure  Yeast  in  Wineries. 

24.  Olive  Pickling. 

25.  Suggestions  Begarding  Examination  of  Lands. 

26.  Selection  and  Preparation  of  Vine  Cuttings. 

27.  Marly  Subsoils  and  the  Chlorosis  or  Yellowing  of  Citrus  Trees. 

Copies  may  be  had  on  Application  to  Director  of  Experiment  Station, 

Berkeley,  Calif. 


